Balloon catheter and guidewire-deployed treatment systems are used to temporarily occlude a vessel in the coronary vasculature during diagnostic and interventional procedures. Guidewires help guide the insertion of catheters and various medical instruments to a desired treatment location within the vasculature of a human body. A flexible guidewire can be advanced through the blood vessels until the guidewire extends across the vessel segment to be treated. Treatment catheters, such as a balloon dilation catheter for PTCA, may be inserted over the guidewire and similarly advanced through the vasculature until they reach the treatment site.
Balloon angioplasty is commonly used to alleviate stenotic lesions in blood vessels, thereby reducing the need for heart bypass operations. Medical balloon catheters also have been proven efficacious in treating a wide variety of blood vessel disorders such as intravascular restrictions due to atherosclerosis or restenosis.
Vascular stenoses, which may be partially or totally occluded, are often characterized by having a mineral component. A variety of different protocols have been developed for treating vascular diseases with these calcified areas. The treatment methodologies generally involve mechanically removing or reducing the size of the stenosis, mechanical debridement, atherectomy, balloon angioplasty, stenting, and bypass surgery procedures.
Intravascular procedures often use one or more catheters, such as balloon catheters to dilate vascular restrictions or atherectomy catheters to remove the restriction. Unfortunately, the intravascular procedures associated with these devices may result in particles being dislodged while the restriction is dilated or cut. Such dislodged particles may move downstream from the area of restriction, possibly causing an embolism, which could compromise the flow of blood to the surrounding tissue.
Treatment procedures using occlusion balloon catheters and aspiration catheters have been developed to help prevent potentially embolic debris from migrating with the blood stream. The occlusion balloon catheter blocks or impedes blood flow while the aspiration catheter aspirates and removes embolic particles from the area of the stenosis.
Some catheter treatment procedures introduce and remove sequentially a number of treatment catheters over a guidewire, the latter acting as a guide for the exchange of one treatment catheter to another. Embolic containment procedures typically employ one or two occlusion balloons in conjunction with an aspiration catheter. One example of an inflatable occlusion catheter includes an occlusion balloon mounted distally on an elongated wire-like shaft that extends through a guidewire lumen of a primary dilation or atherectomy catheter. The balloon is advanced through a vessel, positioned distal to the site of the stenosis, and temporarily inflated to prevent embolic particles from migrating downstream as the occlusive restriction is being dilated or cut. After the restriction has been treated, the primary treatment catheter can be removed from over the guidewire of the occlusion balloon catheter. An aspiration catheter can then be advanced to the treatment site to aspirate any embolic debris generated during the treatment. Once the embolic particles have been aspirated, the occlusion balloon(s) is/are deflated and removed from the patient.
An occlusion catheter is often constructed as a guidewire having a hollow shaft, a flexible, shapeable distal tip, and a deflated elastomeric occlusion balloon attached at the proximal end of the distal tip. During use, the distal tip of the guidewire and the balloon cross the lesion, an inflation device is attached to the proximal end of the catheter, and the occlusion balloon is inflated with dilute contrast agent. Following the inflation of the balloon, an angiogram using fluoroscopy may be taken to ensure complete occlusion by the balloon.
The occlusion guidewire can be used in coordination with other treatment catheters to infuse or deliver fluoroscopic material and therapeutic agents to the treatment site. With the occlusion balloon inflated, balloon angioplasty or stenting may be performed. A handheld inflation device can be removed from the proximal end of the catheter while the occlusion balloon remains inflated, and then a stent-delivery catheter may be exchanged to provide a percutaneous transluminal angioplasty. The embolic particles that are released during a coronary angioplasty or stenting procedure may remain upstream of the inflated occlusion balloon. Following the removal of the angioplasty balloon catheter or stent-delivery catheter, an aspiration catheter may be introduced over the occlusion guidewire to aspirate the particles.
A specific example of an occlusion catheter is described by Rauker and others in “Occlusion Device”, U.S. Pat. No. 6,475,185 issued Nov. 5, 2002. The occlusion device includes an elongated tubular shaft having an inflatable balloon disposed near the distal end of the elongate shaft with a proximal seal of a sufficiently small profile to allow a second catheter to pass over the distal occlusion device while the inflatable balloon remains uninflated. One occlusion device includes an elongated fluid displacement rod within the elongated shaft of the occlusion device, providing both a fluid pressure source and a seal.
Currently used occlusion balloon catheters are able to control the flow of inflation and contrast fluid with sealing members such as plugs or valves located on the proximal end of the catheter. An exemplary catheter valve is a plug consisting of a wire that is formed to provide friction in a hollow guidewire or hypotube with a sealing member on the distal end of the wire. The plug is pushed in and out, which moves the sealing member distal and proximal to an inflation port via frictional pads at the proximal end of the catheter that grip the plug wire. The pads may be moved in conjunction with an adapter knob that is positioned on the hypotube. The inflation port of the hypotube is positioned to line up with the inflation port on the adapter to provide a continuous fluid path to inflate the occlusion balloon. Fluid is transferred through the hypotube to fill the occlusion balloon.
Manufacturers of balloon catheters have developed several types of sealing mechanisms used to control the flow and seal inflation fluid into the occlusion balloon. Sell and others have used a valve of an inner tube that is closely fit into an outer tube, as disclosed in “Low Profile Valve and Balloon Catheter”, U.S. Pat. No. 6,090,083 issued Jul. 18, 2000. The low-profile inflation valve includes a first thermoplastic tube with at least one region of decreased inner diameter, and a structure, which may be a tube, movably located inside the lumen. The region of decreased inner diameter of the first tube forms a seal with a portion of the structure.
Improvements to a valve for a balloon occlusion catheter are proposed in “Low Profile Catheter Valve and Inflation Adaptor”, Zadno-Azizi et al., U.S. Patent Application 2002/0133117 published Sep. 19, 2002; “Exchange Method for Emboli Containment”, Zadno-Azizi et al., U.S. Pat. No. 6,544,276 issued Apr. 8, 2003; “Method of Emboli Protection using a Low Profile Catheter”, Zadno-Azizi et al., U.S. Pat. No. 6,500,166 granted Dec. 31, 2002; and “Low Profile Catheter Valve”, U.S. Pat. No. 6,355,014, Zadno-Azizi et al., granted Mar. 12, 2002. The catheter includes a low-profile catheter valve with a movable sealer portion positioned within the inflation lumen of a catheter. The sealer portion forms a fluid tight seal with the inflation lumen by firmly contacting the entire circumference of a section of the inflation lumen. The sealer portion is positioned proximate to a side-access inflation port on the catheter, establishing an unrestricted fluid pathway between the inflation port and an inflatable balloon on the distal end of the catheter. The sealer portion can be moved to a position distal of the inflation port, thereby preventing fluid from being introduced into or withdrawn from the balloon via the inflation port. An inflation adaptor can be used for moving the sealer portion within the catheter to establish or close the fluid pathway between the inflation port and the inflatable balloon.
A related low-profile catheter valve comprising a movable sealer portion positioned within the inflation lumen of a catheter is described in “Guidewire Inflation System”, Zadno-Azizi et al., U.S. Pat. No. 6,050,972 granted Apr. 18, 2000. The sealer portion forms a fluid tight seal with the inflation lumen by firmly contacting the entire circumference of a section of the inflation lumen. The sealer portion may be positioned proximally of a side-access inflation port on the catheter to establish an unrestricted fluid pathway between the inflation port and an inflatable balloon on the distal end of the catheter. The sealer portion can be moved to a position distal of the inflation port, thereby preventing any fluid from being introduced into or withdrawn from the balloon via the inflation port. In one of the embodiments of the catheter valve, a tubular sealing member is used as a rotary valve mechanism at the distal end of the catheter. The tubular sealer fits tightly within the lumen of the catheter and may rotate within the lumen. Fluid flows through the valve when the tubular sealer rotates within the lumen to align its opening or port to the side-port access of the lumen.
Another description of a valved balloon catheter having a wire with a valve plug slidably disposed within the inflation lumen is described in “Balloon Catheter with Delivery Side Holes”, Kupiecki, U.S. Patent Application 2003/0004461 published Jan. 2, 2003. The valve plug forms an adjustable pressure seal at a valve seat on the distal end of the catheter and allows fluid within the inflation lumen to be pressurized by a fluid source in order to facilitate balloon inflation.
Recent research continues to address the need for an improved valve system with more control over fluid flow to and from an occlusion balloon positioned within a vessel in a body. The desirable valve has a more reliable sealing member that does not require careful alignment of a sealer portion of a valve with small inflation holes in a hypotube. The desirable valve also does not require hard-to-control axial movement of the sealer portion during actuation. Therefore, an improved valve for a balloon catheter system is desirable for catheter-employed treatments for vessels in the body, providing greater control of fluid through a catheter, and increased utility and performance of associated medical devices used during the treatment of vascular conditions.